Rotary actuator

ABSTRACT

A rotary actuator includes: an electric motor; a case that receives the electric motor; a rotatable body that is configured to transmit an output of the electric motor to an outside of the case; a seal member that seals between the rotatable body and the case; and a labyrinth forming portion that forms a labyrinth space in a path that extends from an outside space of the case to a sealing point of the rotatable body, at which the rotatable body is sealed by the seal member.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No.16/390,273, filed on Apr. 22, 2019, which is a continuation applicationof International Patent Application No. PCT/JP2017/040738 filed on Nov.13, 2017, which designated the U.S. and claims the benefit of priorityfrom Japanese Patent Application No. 2016-222161 filed on Nov. 15, 2016.The entire disclosures of all of the above applications are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a rotary actuator.

BACKGROUND

Previously, there is known a rotary actuator that is used as a drivedevice of a shift-by-wire system of a vehicle. At the rotary actuator,an electric motor is received in a case, and a manual shaft of atransmission is fitted to an output shaft of the rotary actuator.

SUMMARY

According to the present disclosure, a rotary actuator includes anelectric motor; a case that receives the electric motor; a rotatablebody that is configured to transmit an output of the electric motor toan outside of the case; a seal member that seals between the rotatablebody and the case; and a labyrinth forming portion that forms alabyrinth space in a path that extends from an outside space of the caseto a sealing point of the rotatable body, at which the rotatable body issealed by the seal member.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure, together with additional objectives, featuresand advantages thereof, will be best understood from the followingdescription in view of the accompanying drawings.

FIG. 1 is a schematic diagram showing a shift-by-wire system, in which arotary actuator of a first embodiment is applied.

FIG. 2 is a descriptive diagram for describing a shift range changemechanism shown in FIG. 1.

FIG. 3 is a cross sectional view of the rotary actuator shown in FIG. 1.

FIG. 4 is a partial enlarged view of a portion IV in FIG. 3.

FIG. 5 is an enlarged view showing a peripheral area around an outputshaft of a rotary actuator of a second embodiment.

FIG. 6 is an enlarged view showing a peripheral area around an outputshaft of a rotary actuator of a third embodiment.

FIG. 7 is a cross sectional view taken along line VII-VII in FIG. 6.

FIG. 8 is a diagram showing a state where a mount angle on the vehicleis deviated about 90 degrees in one circumferential direction from abasic mount state on the vehicle shown in FIG. 7.

FIG. 9 is a diagram showing a state where the mount angle on the vehicleis deviated about 90 degrees in the other circumferential direction fromthe basic mount state on the vehicle shown in FIG. 7.

FIG. 10 is a diagram showing a state where an installation angle of acap relative to a case is deviated in the one circumferential directionfrom a basic installation state shown in FIG. 7.

FIG. 11 is a diagram showing a state where the installation angle of thecap relative to the case is deviated in the other circumferentialdirection from the basic installation state shown in FIG. 7.

FIG. 12 is an enlarged view showing a peripheral area around an outputshaft of a rotary actuator of a fourth embodiment.

FIG. 13 is an enlarged view showing a peripheral area around an outputshaft of a rotary actuator of a fifth embodiment.

FIG. 14 is a diagram showing a state where the vehicle is tilted towardone side from the basic mount state on the vehicle shown in FIG. 13.

FIG. 15 is a diagram showing a state where the vehicle is tilted towardthe other side from the basic mount state on the vehicle shown in FIG.13.

FIG. 16 is a transverse cross sectional view of an output shaft of arotary actuator of another embodiment.

DETAILED DESCRIPTION

Previously, there has been proposed a rotary actuator that is used as adrive device of a shift-by-wire system of a vehicle. At the rotaryactuator, an electric motor is received in a case, and a manual shaft ofa transmission is fitted to an output shaft of the rotary actuator. Theoutput shaft and the manual shaft form a rotatable body, and a sealmember is placed between the case and the rotatable body. The sealmember limits intrusion of liquid, such as water, or a foreign objectfrom an outside space into an inside of the case.

At the rotary actuator, corrosion may possibly occur at an exposedportion of the rotatable body that is located on the outside space sideof a sealing point, at which the rotatable body is sealed by the sealmember. Thereby, a gap may be formed between the rotatable body and theseal member upon elapse of time, and the water or a foreign object maypossibly intrude into an area of the electric motor at the inside of thecase.

A rotary actuator of the present disclosure includes an electric motor;a case that receives the electric motor; a rotatable body that isconfigured to transmit an output of the electric motor to an outside ofthe case; a seal member that seals between the rotatable body and thecase; and a labyrinth forming portion that forms a labyrinth space in apath that extends from an outside space of the case to a sealing pointof the rotatable body, at which the rotatable body is sealed by the sealmember.

By providing the labyrinth space in the path, which extends from theoutside space to the sealing point, application of water to the sealingpoint and its peripheral area is reduced. Therefore, the gap is lesslikely formed between the rotatable body and the seal member upon elapseof time, and thereby intrusion of the water or the foreign object intothe inside of the case can be limited.

Hereinafter, embodiments will be described with reference to thedrawings. Substantially identical features among the embodiments areindicated by the same reference signs and will not be describedredundantly.

First Embodiment

FIG. 1 shows a rotary actuator (hereinafter referred to as an actuator)according to a first embodiment. The actuator 10 is used as a drivedevice of a shift-by-wire system 11 of a vehicle.

Structure of Shift-By-Wire System

First of all, a structure of the shift-by-wire system 11 will bedescribed with reference to FIG. 1. The shift-by-wire system 11includes: a shift manipulator 13 that is configured to command a shiftrange of a transmission 12 of the vehicle; an actuator 10 that isconfigured to drive a shift range change mechanism 14 of thetransmission 12; a drive circuit 15 of the actuator 10; an inhibitorswitch 16 that is configured to sense a rotational position of a manualshaft 26, which is rotated integrally with an output shaft of theactuator 10; and a control circuit 17. The control circuit 17 controlsthe drive circuit 15 according to a command signal of the shift rangeand thereby drives the actuator 10.

As shown in FIG. 2, the shift range change mechanism 14 includes: arange change valve 20 that is configured to control supply of ahydraulic pressure to a hydraulic operating mechanism placed in thetransmission 12; a detent spring 21 and a detent lever 22 that areconfigured to hold the current shift range; a park rod 25 that isconfigured to lock rotation of the output shaft of the transmission 12by fitting a park pole 24 to a park gear 23 of the output shaft at thetime of shifting the shift range to a parking range; and a manual shaft26 that is configured to rotate integrally with the detent lever 22.

The shift range change mechanism 14 rotates the detent lever 22 togetherwith the manual shaft 26 to place each of the range change valve 20 andthe park rod 25, which are coupled to the detent lever 22, to acorresponding position that corresponds to a target shift range. Theshift-by-wire system 11 includes an actuator 10 that is directly coupledto the manual shaft 26 to electrically change the shift range.

Structure of Actuator

Next, a structure of the actuator 10 will be described with reference toFIGS. 1 and 3. The actuator 10 includes: an electric motor 30 thatserves as a drive source; a speed reducing mechanism 31 that isconfigured to transmit a rotational drive force of the electric motor 30to the shift range change mechanism 14; and a case 32 that receives theelectric motor 30 and the speed reducing mechanism 31.

The case 32 includes a first case portion 33 and a second case portion34, which are respectively shaped into a cup form. The first caseportion 33 and the second case portion 34 are fixed together by bolts 37and define a receiving space 38 that receives the electric motor 30 andthe speed reducing mechanism 31.

A bracket 39 is provided to an opposite side of the second case portion34, which is opposite from the first case portion 33, while the bracket39 is fixed to the second case portion 34 by the bolts 37. The actuator10 is fixed to a transmission case 42 by bolts 41 that are insertedthrough the bracket 39.

The second case portion 34 includes a tubular projecting portion 35 thatprojects from a bottom part of the second case portion 34 in an axialdirection. The manual shaft 26 projects into an inside of the tubularprojecting portion 35 through a through hole 43 of the transmission case42.

The electric motor 30 includes: a stator 51 that is fixed to the firstcase portion 33; a rotor 52 that is placed on a radially inner side ofthe stator 51; and a rotatable shaft 53 that is rotated together withthe rotor 52 about a rotation axis AX1.

One end portion 54 of the rotatable shaft 53 is supported by a bearing55, and the other end portion 56 of the rotatable shaft 53 is supportedby a bearing 57. The bearing 55 is provided at a center of a bottom partof the first case portion 33. The bearing 57 is provided at an inside ofan output shaft 63 described later.

A rotor fitting portion 58, to which the rotor 52 is fitted, and aneccentric portion 59, which is eccentric to the rotation axis AX1, areprovided between the one end portion 54 and the other end portion 56.The one end portion 54, the other end portion 56, the rotor fittingportion 58 and the eccentric portion 59 are formed integrally in onepiece by a common member.

The control circuit 17 controls an electric current supplied tothree-phase windings 511 of the stator 51, so that the electric motor 30can be rotated in both of two opposite directions and can be stopped ata desirable position.

The speed reducing mechanism 31 includes an internal gear 61, aplanetary gear 62 and the output shaft 63. The internal gear 61 iscoaxial with the rotational axis AX1 and is fixed to the second caseportion 34. The planetary gear 62 is supported by a bearing 64 in amanner that enables rotation of the planetary gear 62 about theeccentric axis AX2 while the planetary gear 62 is meshed with theinternal gear 61 at an inside of the internal gear 61. The bearing 64 isprovided on an outer side of the eccentric portion 59. When therotatable shaft 53 is rotated, the planetary gear 62 has a planetarymotion, i.e., the planetary gear 62 revolves around the rotation axisAX1 and rotates about the eccentric axis AX2. At this time, therotational speed of the planetary gear 62 is reduced in comparison to arotational speed of the rotatable shaft 53. The planetary gear 62includes a plurality of engaging projections 65 that are provided totransmit the rotation and project in the axial direction.

The output shaft 63 is coaxial with the rotational axis AX1 and includesa shaft portion 67, which is supported by a bearing 66 in a manner thatenables rotation of the shaft portion 67 about the rotation axis AX1;and a flange 68 that outwardly projects from the shaft portion 67. Thebearing 66 is placed at an inside of a base end part of the tubularprojecting portion 35. The flange 68 includes a plurality of engagingholes 69 that are provided to transmit the rotation and respectivelyreceive the engaging projections 65 of the planetary gear 62. Therotation of the planetary gear 62 is transmitted to the output shaft 63through the engagement between the engaging projections 65 and theengaging holes 69.

A blind hole 71 is formed at one end portion of the shaft portion 67,which is located on the electric motor 30 side. The bearing 57 isprovided in the blind hole 71. A fitting hole 72, which is a blind hole,is formed at the other end portion of the shaft portion 67 located onthe transmission case 42 side. The fitting hole 72 is a spline hole. Anend portion of the manual shaft 26, which is located on the actuator 10side, is formed as a spline shaft and is inserted into the fitting hole72, so that the manual shaft 26 is coupled to the output shaft 63 in amanner that enables transmission of the rotation between the outputshaft 63 and the manual shaft 26. The output shaft 63 and the manualshaft 26 serve as a rotatable body that is configured to transmit anoutput of the electric motor 30 to an outside of the case 32. A sealmember 73 is provided between the shaft portion 67 of the output shaft63 and the tubular projecting portion 35. The seal member 73 sealsbetween the rotatable body discussed above and the case 32.

Structure Around Output Shaft

Next, a structure around the output shaft 63 will be described withreference to FIG. 4. An outer diameter D1 of the shaft portion 67 of theoutput shaft 63 is larger than an outer diameter D2 of the manual shaft26. Therefore, a fitting portion, at which the output shaft 63 and themanual shaft 26 are fitted together, forms a stepped shaft portion 75that is a shaft portion shaped into a stepped form. The stepped shaftportion 75 includes a large diameter portion 76, which is formed by theend portion of the shaft portion 67, and a small diameter portion 77,which is a portion of the manual shaft 26. The output shaft 63 is sealedby the seal member 73 at a sealing point 78 of the output shaft 63, andthe stepped shaft portion 75 is located on a side of the sealing point78 where the outside space 79 of the case 32 is located. The largediameter portion 76 is positioned on a side of the small diameterportion 77 where the sealing point 78 is placed. Specifically, the largediameter portion 76 and the small diameter portion 77 are arranged oneafter the other in this order form the sealing point 78 side.

A cap 81 is installed to the tubular projecting portion 35 of the case32. The cap 81 includes: a tubular fitting portion 82, which is fittedto an outer side of the tubular projecting portion 35; and a ringportion 83, which radially inwardly projects from the tubular fittingportion 82 toward the small diameter portion 77. An inner diameter D3 ofthe ring portion 83 is smaller than the outer diameter D1 of the largediameter portion 76.

With this structure, a labyrinth space 84 is formed in a path thatextends from the outside space 79 of the case 32 to the sealing point 78of the output shaft 63. Specifically, the labyrinth space 84 is formedbetween an inner wall surface 85 of the ring portion 83 and an outerwall surface 86 of the small diameter portion 77 and also between a sidewall surface 87 of the ring portion 83 and an end surface 88 of thelarge diameter portion 76. The term “labyrinth” means that a start pointand an end point cannot be connected by a linear path, and at least onebent portion is present in the labyrinth path. The actuator 10 includesa labyrinth forming portion 89 that forms the labyrinth space 84.

Advantages

As discussed above, in the first embodiment, the actuator 10 includes:the seal member 73 that seals between the output shaft 63 (serving asthe rotatable body) and the tubular projecting portion 35 of the case32; and the labyrinth forming portion 89 that forms the labyrinth space84 in the path that extends from the outside space 79 of the case 32 tothe sealing point 78 of the output shaft 63.

By providing the labyrinth space 84 in the path that extends from theoutside space 79 to the sealing point 78, application of water to thesealing point 78 and a peripheral area around the sealing point 78 isreduced. Therefore, a gap is less likely formed between the output shaft63 and the seal member 73 upon elapse of time, and thereby intrusion ofthe water or the foreign object(s) into the inside of the case 32 can belimited. In this way, it is possible to avoid a trouble(s) that iscaused by the intrusion of the water and/or the foreign object(s)particularly to the area of the electric motor 30 at the inside of thecase 32.

Now, a comparative example, in which the inhibitor switch is notprovided between the actuator and the transmission case, will bediscussed. In this comparative example, the case of the actuator isfitted to the transmission case, and a seal member, such as an O-ring,may be provided at a fitting point, at which the case of the actuator isfitted to the transmission case. In this way, a sealing point, which islocated between the case and the output shaft or the manual shaft, and asurround area around the sealing point will not be exposed to theoutside space.

However, like in the first embodiment where the inhibitor switch 16 isprovided between the actuator 10 and the transmission case 42, thesealing point 78 of the output shaft 63 and its peripheral area areunavoidably exposed to the outside space 79. Even in such a case, byproviding the labyrinth space 84 in the path that extends from theoutside space 79 to the sealing point 78, the application of the waterto the sealing point 78 and its peripheral area can be reduced.

Second Embodiment

In a second embodiment, as shown in FIG. 5, a tubular projecting portion101 of the case 32 and a tubular fitting portion 102 of the cap 81 forma drain passage 104. The drain passage 104 is a space in an inside ofthe tubular projecting portion 101 and communicates a space 103, whichis located between the sealing point 78 and the labyrinth space 84, tothe outside space 79. The drain passage 104 includes: an inner drainhole 105 of the tubular projecting portion 101; and a drain groove 106and an outer drain hole 107 of the tubular fitting portion 102. Theinner drain hole 105 is a through hole that extends through the tubularprojecting portion 101 between an inside and an outside of the tubularprojecting portion 101. The outer drain hole 107 is a through hole thatextends through the tubular fitting portion 102 between an inside and anoutside of the tubular fitting portion 102. The drain groove 106 isformed at an outer wall of the tubular projecting portion 101 andcommunicates between the inner drain hole 105 and the outer drain hole107. In the second embodiment, the number of the inner drain hole 105 isone, and the number of the outer drain hole 107 is one. Furthermore, anaxial position of the outer drain hole 107 is displaced from an axialposition of the inner drain hole 105.

With the above structure, the drain passage 104 becomes a passage in alabyrinth form. A tubular portion 109, which includes the tubularprojecting portion 101 and the tubular fitting portion 102, forms thelabyrinth forming portion 108 and includes the drain passage 104 thatcommunicates between the space 103 and the outside space 79. The tubularprojecting portion 101 serves as the small diameter tube, and thetubular fitting portion 102 serves as the large diameter tube.

Advantages

In the first embodiment, it is difficult for the water or the like toenter from the outside space 79 into the inside space of the tubularprojecting portion 101 due to the provision of the labyrinth space 84.However, once the water or the like enters into the inside space of thetubular projecting portion 101, it stays in the inside space of thetubular projecting portion 101.

With respect to this point, in the second embodiment, the labyrinthforming portion 108 includes the tubular portion 109 that is placed onthe outside space 79 side of the sealing point 78 and on the radiallyouter side of the output shaft 63. The tubular portion 109 includes thedrain passage 104 that communicates the space 103, which is locatedbetween the sealing point 78 and the labyrinth space 84, to the outsidespace 79.

Thereby, the water or the like, which has entered into the space 103, isdrained to the outside space 79 through the drain passage 104.Therefore, the application of the water to the sealing point 78 and itssurrounding area can be further reduced.

Furthermore, in the second embodiment, the drain passage 104 is thepassage in the labyrinth form. Therefore, it is difficult for the wateror the like to enter into the space 103 from the outside space 79 sidethrough the drain passage 104.

Furthermore, in the second embodiment, the tubular portion 109 includesthe tubular projecting portion 101 and the tubular fitting portion 102while the tubular fitting portion 102 is fitted to the outer side of thetubular projecting portion 101. The drain passage 104 includes: theinner drain hole 105 that extends through the tubular projecting portion101 between the inside and the outside of the tubular projecting portion101; the outer drain hole 107 that extends through the tubular fittingportion 102 between the inside and the outside of the tubular fittingportion 102; and the drain groove 106 that is formed at the outer wallof the tubular projecting portion 101 and communicates between the innerdrain hole 105 and the outer drain hole 107. The axial position of theouter drain hole 107 is displaced from the axial position of the innerdrain hole 105. With this construction, the drain passage 104 can beformed as the passage in the labyrinth form.

Third Embodiment

In a third embodiment, as shown in FIGS. 6 and 7, a labyrinth formingportion 111 includes a tubular portion 114 that has a tubular projectingportion 112 and a tubular fitting portion 113. The tubular portion 114includes a drain passage 118 that has a plurality of inner drain holes115, a drain groove 116 and a plurality of outer drain holes 117. Theinner drain holes 115 are respectively formed at two locations, whichare circumferentially spaced from each other. The outer drain holes 117are respectively formed at three locations, which are circumferentiallyspaced from each other. The drain groove 116 is formed at the tubularprojecting portion 112 and extends in the circumferential direction.

Hereinafter, when the inner drain holes 115 need to be distinguishedfrom one another, the inner drain holes 115 will be indicated as aninner drain hole 115A and a inner drain hole 115B, respectively. Also,when the outer drain holes 117 need to be distinguished from oneanother, the outer drain holes 117 will be indicated as an outer drainhole 117A, an outer drain hole 117B and an outer drain hole 117C,respectively.

In a transverse cross section (i.e., FIG. 7) of the tubular projectingportion 112, which includes the inner drain holes 115, a straight line,which is imaginary and externally touches the shaft portion 67 of theoutput shaft 63, is defined as an imaginary straight line L, and theimaginary straight line L intersects with an inner wall surface 119 ofthe tubular projecting portion 112 at one intersection point and anotherintersection point, which are defined as a first intersection point P1and a second intersection point P2, respectively. A circumferentialdistance A1 between the two inner drain holes 115, which arecircumferentially arranged one after the other, is smaller than acircumferential distance A2 between the first intersection point P1 andthe second intersection point P2.

Here, in an axial view (i.e., FIG. 7) taken from the output shaft 63side toward the manual shaft 26 side, a clockwise direction will bereferred to as one circumferential direction, and a counterclockwisedirection will be referred to as the other circumferential direction. Atthis time, the outer drain holes 117, the inner drain holes 115 and thedrain groove 116 have the following positional relationships.

First Positional Relationship

One 117A of the outer drain holes 117, which is furthermost toward oneside in the one circumferential direction among the outer drain holes117, is displaced in the one circumferential direction away from one115A of the inner drain holes 115, which is furthermost toward the oneside in the one circumferential direction among the inner drain holes115.

Second Positional Relationship

Another one 117C of the outer drain holes 117, which is furthermosttoward the other side in the other circumferential direction among theouter drain holes 117, is displaced in the other circumferentialdirection away from another one 1156 of the inner drain holes 115, whichis furthermost toward the other side in the other circumferentialdirection among the inner drain holes 115.

Third Positional Relationship

The drain groove 116 extends toward the one side in the onecircumferential direction further away from the one 115A of the innerdrain holes 115, which is furthermost toward the one side in the onecircumferential direction among the inner drain holes 115. The draingroove 116 extends toward the other side in the other circumferentialdirection further away from the other one 1156 of the inner drain holes115, which is furthermost toward the other side in the othercircumferential direction among the inner drain holes 115.

Fourth Positional Relationship

A circumferential length A3 of the drain groove 116 is larger than acircumferential distance A4 between: the one 117A of the outer drainholes 117, which is furthermost toward the one side in the onecircumferential direction among the outer drain holes 117; and the otherone 117C of the outer drain holes 117, which is furthermost toward theother side in the other circumferential direction among the two outerdrain holes 117.

Advantages

As discussed above, in the third embodiment, the inner drain holes 115are respectively formed at the two or more locations, which arecircumferentially spaced from each other. Therefore, even if the mountstate of the actuator 10 on the vehicle is deviated to some extent asshown in FIGS. 7 to 9, at least one of the inner drain holes 115 islocated on the lower side of the shaft portion 67 of the output shaft 63in the vertical direction. A permissible angle at this time is largerthan that of a case where only one inner drain hole 115 is provided.Therefore, the state, in which the sealing point 78 and its peripheralarea is not immersed in the water or the like area, can be maintained asmuch as possible. In the present embodiment, the state of avoiding theapplication of the water can be maintained even when the actuator 10 isrotated by 180 degrees from the state shown in FIG. 8 to the state shownin FIG. 9, and thereby the permissible angle discussed above is equal toor lager than 180 degrees.

Furthermore, in the third embodiment, the circumferential distance A1between the two inner drain holes 115, which are arranged one after theother in the circumferential direction, is smaller than thecircumferential distance A2 between the first intersection point P1 andthe second intersection point P2. Thereby, the state of avoiding theapplication of the water can be continuously maintained regardless ofthe mount angle on the vehicle. Specifically, even when the mount angleon the vehicle is deviated, at least one of the inner drain holes 115 islocated on the lower side of the shaft portion 67 of the output shaft 63in the vertical direction.

Furthermore, in the third embodiment, the first positional relationshipand the second positional relationship are satisfied. In this way, evenwhen the mount angle on the vehicle is deviated from the basic mountstate on the vehicle shown in FIG. 7 to another mount angle on thevehicle shown in FIG. 8 or FIG. 9, the water or the like can be smoothlydrained through the drain passage 118.

Furthermore, in the third embodiment, the third positional relationshipis satisfied. In this way, even when the mount angle on the vehicle isdeviated from the basic mount state on the vehicle shown in FIG. 7 toanother mount angle on the vehicle shown in FIG. 8 or FIG. 9, the wateror the like can be smoothly drained through the drain passage 118.

Furthermore, in the third embodiment, the drain groove 116 is formed atthe tubular projecting portion 112. Also, the fourth positionalrelationship is satisfied. In this way, even when the installation ofthe cap 81 to the case 32 is deviated, i.e., even when the relativerotational position between the tubular fitting portion 113 and thetubular projecting portion 112 is deviated from the basic installationstate shown in FIG. 7 to the installation state shown in FIG. 10 or FIG.11, the inner drain hole(s) 115 and the outer drain hole(s) 117 can beconnected relative to each other through the drain groove 116.

Fourth Embodiment

In a fourth embodiment, as shown in FIG. 12, a manual shaft 121 includesa flange 122 that is placed on the radially inner side of the ringportion 83. A side wall 123 of the flange 122, which is opposite fromthe sealing point 78, is located on the sealing point 78 side of a sidewall 124 of the ring portion 83, which is opposite from the sealingpoint 78. The output shaft 63 serves as a first shaft, and the manualshaft 121 serves as a second shaft.

Advantages

By providing the flange 122 in the above described manner, the water orthe like, which flows along the manual shaft 121 toward the labyrinthspace 84, is blocked by the flange 122. Therefore, it is difficult forthe water or the like to enter from the outside space 79 side into thespace 103 through the labyrinth space 84, and thereby the application ofthe water to the sealing point 78 and its peripheral area can be furtherreduced.

Fifth Embodiment

In a fifth embodiment, as shown in FIG. 13, a labyrinth forming portion131 includes the tubular projecting portion 35, a first annularprojection 132 and a second annular projection 133. The first annularprojection 132 is located on a radially outer side of the tubularprojecting portion 35 and projects from a switch case 134 of theinhibitor switch 16 toward the case 32 while an axial extent of thefirst annular projection 132 overlaps with an axial extent of thetubular projecting portion 35. The second annular projection 133 islocated on a radially inner side of the tubular projecting portion 35and projects from the switch case 134 toward the case 32 while an axialextent of the second annular projection 133 overlaps with an axialextent of the tubular projecting portion 35.

A labyrinth space 140 is formed between an inner wall surface 135 of thefirst annular projection 132 and an outer wall surface 136 of thetubular projecting portion 35 and also between a distal end surface 137of the tubular projecting portion 35 and a side wall surface 138 of theswitch case 134. A lower side of the first annular projection 132, whichis placed at the lower side in the vertical direction in a state wherethe rotary actuator is installed to the vehicle, has a cutout 139. Theswitch case 134 serves as a support member.

Advantages

As discussed above, in the path, which extends from the outside space 79to the sealing point 78, the labyrinth space 140 is placed between thecase 32 and the switch case 134. Thereby, application of the water tothe sealing point 78 and its peripheral area is reduced. For example, ina case where the vehicle is tilted in a manner shown in FIG. 14, thewater or the like falls downward along an outer wall surface of thefirst annular projection 132. Also, in a case where the vehicle istilted in a manner shown in FIG. 15, even when the water or the likeflows along an outer wall surface of the tubular projecting portion 35and intrudes into the labyrinth space 140, the water or the like flowsdownward along the outer wall surface of the second annular projection133 and falls downward through the cutout 139.

Other Embodiments

In another embodiment, as shown in FIG. 16, the drain groove is notformed at a tubular projecting portion 151, and a drain groove 153 maybe formed at an inner wall of a tubular fitting portion 152.

In another embodiment, the stepped shaft portion may be formed only bythe output shaft or only by the manual shaft. Furthermore, the steppedshaft portion may be formed by a projection in a flange form.

In another embodiment, an outer diameter of the shaft portion of theoutput shaft may be smaller than an outer diameter of the manual shaft.In another embodiment, a seal member may be placed between the case andthe manual shaft.

In another embodiment, the tubular fitting portion of the cap may befitted to an inner side of the tubular projecting portion of the case.Furthermore, the cap may be formed only by the ring portion and may befixed to the end portion of the tubular projecting portion of the case.

In another embodiment, the inner drain holes may be arranged at equalintervals or unequal intervals along an entire circumferential extent ofthe tubular projecting portion, and the drain groove may extend alongthe entire circumferential extent.

In the fifth embodiment, the first annular projection 132 and the secondannular projection 133 are provided, and the cutout 139 is formed at thefirst annular projection 132. Alternatively, in another embodiment, oneor both of the second annular projection and the cutout may beeliminated.

The present disclosure is not necessarily limited to the aboveembodiments and may be implemented in various forms without departingfrom the principle of the present disclosure.

The present disclosure has been described in view of the variousembodiments. However, the present disclosure should not be limited tothe above embodiments and the structures described therein. The presentdisclosure covers various modifications and equivalents thereof. Also,various combinations and forms, as well as other combinations and formsincluding one element only, one or more, or even less, among them, fallwithin the scope and spirit of the present disclosure.

The invention claimed is:
 1. A rotary actuator as a drive device of ashift-by-wire system for a vehicle, comprising: an electric motor; acase that receives the electric motor; a shaft that is configured totransmit an output of the electric motor to an outside of the case; aseal that seals between the shaft and the case; and a labyrinth formingportion that forms a labyrinth space in a path that extends from anoutside space of the case to a sealing point of the shaft, wherein: thesealing point is a point where the shaft is sealed by the seal; thelabyrinth forming portion includes a tubular portion that is formedseparately from the seal and is placed on a radially outer side of theshaft and also on a radially outer side of the sealing point where theoutside space is placed; the tubular portion includes a drain passage,wherein the drain passage is a space in an inside of the tubular portionand communicates a space, wherein the space is located between thesealing point and the labyrinth space, to the outside space; the drainpassage is a passage in a form of a labyrinth; the tubular portionentirely circumferentially surrounds the seal and has an innerperipheral surface and an outer peripheral surface that are opposed toeach other in a radial direction and are placed on a radially outer sideof the seal; an outer opening of the drain passage opens at the outerperipheral surface of the tubular portion, and an inner opening of thedrain passage opens at the inner peripheral surface of the tubularportion at a location placed on one axial side of the seal that isaxially opposite from the electric motor; and the seal radially contactsboth the shaft and the inner peripheral surface of the tubular portionall around the shaft.
 2. The rotary actuator according to claim 1,wherein: the tubular portion includes a small diameter tube and a largediameter tube while the large diameter tube is fitted to an outer sideof the small diameter tube; the drain passage includes: an inner drainhole that extends through the small diameter tube from an inside to anoutside of the small diameter tube and has the inner opening; an outerdrain hole that extends through the large diameter tube from an insideto an outside of the large diameter tube and has the outer opening; anda drain groove that is formed at an outer wall of the small diametertube or an inner wall of the large diameter tube, wherein the draingroove communicates between the inner drain hole and the outer drainhole; and one or both of a circumferential position and an axialposition of the outer drain hole are displaced relative to the innerdrain hole.
 3. The rotary actuator according to claim 2, wherein theinner drain hole is one of at least two inner drain holes that arecircumferentially spaced from each other.
 4. The rotary actuatoraccording to claim 3, wherein: the small diameter tube include the atleast two inner drain holes; in a transverse cross section of the smalldiameter tube, an imaginary straight line is defined as an imaginarystraight line that externally touches the shaft, and the imaginarystraight line intersects an inner wall surface of the small diametertube at one intersection point and another intersection point of theimaginary straight line, and the one intersection point and the anotherintersection point of the imaginary straight line are defined as a firstintersection point and a second intersection point, respectively; the atleast two inner drain holes are circumferentially arranged one afteranother; and a circumferential distance between the at least two innerdrain holes is smaller than a circumferential distance between the firstintersection point and the second intersection point.
 5. The rotaryactuator according to claim 3, wherein: the outer drain hole is one ofat least two outer drain holes that are circumferentially spaced fromeach other; one of the at least two outer drain holes is furthermosttoward one side in one circumferential direction among the at least twoouter drain holes and is displaced in the one circumferential directionaway from one of the at least two inner drain holes, wherein the one ofthe at least two inner drain holes is furthermost toward the one side inthe one circumferential direction among the at least two inner drainholes; and another one of the at least two outer drain holes isfurthermost toward another side in another circumferential directionamong the at least two outer drain holes and is displaced in the anothercircumferential direction away from another one of the at least twoinner drain holes, wherein the another one of the at least two innerdrain holes is furthermost toward the another side in the anothercircumferential direction among the at least two inner drain holes. 6.The rotary actuator according to claim 3, wherein: the drain grooveextends toward one side in one circumferential direction further awayfrom one of the at least two inner drain holes, wherein the one of theat least two inner drain holes is furthermost toward the one side in theone circumferential direction among the at least two inner drain holes;and the drain groove extends toward another side in anothercircumferential direction further away from another one of the at leasttwo inner drain holes, wherein the another one of the at least two innerdrain holes is furthermost toward the another side in the anothercircumferential direction among the at least two inner drain holes. 7.The rotary actuator according to claim 2, wherein: the drain groove isformed at the small diameter tube; the outer drain hole is one of atleast two outer drain holes that are circumferentially spaced from eachother; and a circumferential length of the drain groove is larger than acircumferential distance between: one of the at least two outer drainholes, wherein the one of the at least two outer drain holes isfurthermost toward one side in one circumferential direction among theat least two outer drain holes; and another one of the at least twoouter drain holes, wherein the another one of the at least two outerdrain holes is furthermost toward another side in anothercircumferential direction among the at least two outer drain holes. 8.The rotary actuator according to claim 2, wherein: the drain groove isformed at the large diameter tube; the outer drain hole is one of atleast two outer drain holes that are circumferentially spaced from eachother; and a circumferential length of the drain groove is larger than acircumferential distance between: one of the at least two outer drainholes, wherein the one of the at least two outer drain holes isfurthermost toward one side in one circumferential direction among theat least two outer drain holes; and another one of the at least twoouter drain holes, wherein the another one of the at least two outerdrain holes is furthermost toward another side in anothercircumferential direction among the at least two outer drain holes.